Indanthrene monosulfonic acid and process of making same.



rat- RENE IBOHN, .OF MANNHEIM, GERMANY, ASSIGNDR TU BAIJTSGHE AIRTILIN tit $01M. FABRIK, 0F LUDWIGSHAFEN-ON-THE-RIIINE, GrElRIMElNlil', A. CUIEtlPOIFtALTION.

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Specification of Letters Patent. Application filed. September 23, 1909. ficrial No. 519,193.

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To all whom it may concern:

Be it known that I, RENE Bonn, doctor of ysahilosophy andchemist, a citizen of the wiss Republic, residing at Mannheim, Germany, have invented new and useful Improvements in Indanthrene Monosulfonic Acid and Processes of Making Same, of which the following is a specification.

In the specification of Letters Patent No. 692,762 is described the production of a sulfonic acid of indanthrene blue either by melting beta-amino-anthraquinone sulfonic acid with caustic alkali, or by treatingindanthrene with fuming Sulfuric acid. The sulfonic acid so obtained is described as being soluble in water (the solution being greenish blue) and as dyeing animal fiber greenish blue. I have now discovered that by treat ing indanthrene blue with milder sulfonat ing agents, for instance with sulfuric acid monohydrate, or with ordinary concentrated sulfuric acid containing about 95 per cent.

I'I SO,, and preferably in the presence of boric acid, an indanthrene sulfonic acid can beobtained which is difierent from that de scribed in the aforesaid specification, since 't is difficultly soluble in water (the solution being reddish blue) and dyes animal fiber in v d uce one part 0 powdered indanthrene blue,

even and deep brilliant blue shades. The roduct obtainable according to the resent lnvention is a monosulfonic acid, wh1 e that obtainable according to the aforesaid Letters Patent No. 692,762 is a disulfonic acid.

When boric acid is used during the process of sulfonation according to my invention, better yields are obtained than are produced when no boric acid is employed.

The followin% is an example of how m invention may e carried into practical eitfect, but the invention is not confined to this example. The arts are by weight. Introat a temperature ofthirty degrees centigrade, lnto a solution of one part of anhydrous boric acid'in five parts of sulfuric acid monocent. free 80 With alkaline hyc rosul be it yields a cornfiower blue colored rat.

N ow what It claim is 1 1. The process of producing.indanthrene monosulfonic acid by treating indanthrene blue with a mild sulfonating agentsubstam tially as described.

2. The process of making indanthrenel monosulfonic acid by heating indanthrene blue with sulfuric acid. 'monohydrate and anhydrous boric acid.

3. As a new article of manufacture 'indanthrene monosulfonic acid which is dillicultlyL soluble in water, the solution being reddis blue, which yieldsa clear olive solution in concentrated sulfuric acid, a dull olivebrown solution in 23 per cent. fuming sulfuric acid, and dyes animal fiber deep and brilliant blue shades.

Intestimony whereof'li have hereuntoset my hand in the presence of two subscribing witnesses.

RENE Bonn.

Witnesses J. Anne. LLorn, KA'rnI Krnorrnonr.

When the mixture is 

